CN106943899B - A kind of hydrophilic polysulfone membrane and preparation method thereof - Google Patents

Abstract

The invention relates to a hydrophilic polysulfone membrane and a preparation method thereof, which is characterized in that the hydrophilic polysulfone membrane consists of a composite membrane consisting of polysulfone polymer and acrylonitrile-maleic anhydride polymer and a dopamine layer coated on the composite membrane. The polysulfone polymer is used as a membrane material, and a small amount of acrylonitrile-maleic anhydride polymer is added into the membrane-making liquid, so that the hydrophilicity of the polymer can be obviously improved due to the fact that the polymer contains a large amount of carboxyl. And then, dopamine is coated for multiple times, so that the hydrophilic performance of the membrane is further improved, the pore diameter of the membrane is further reduced, the hydrophilicity of the membrane is obviously improved after modification, and the pore diameter of the membrane is changed from ultrafiltration to nanofiltration. The nanofiltration membrane can allow inorganic salt and micromolecules to pass through and retain dye macromolecules, can be applied to the dye desalination process, and the modified membrane is used for direct red dye desalination, and has the retention rate of 80-99%.

Description

A kind of hydrophilic polysulfone membrane and preparation method thereof

technical field

The invention relates to the field of preparation of organic membranes, in particular to a hydrophilic polysulfone membrane and a preparation method thereof, that is, research on hydrophilic modification of polysulfone membrane and modification of its pore size.

Background technique

The dye industry is an important part of the chemical industry, and it occupies an important position in the national economy. The traditional production process not only produces a large amount of waste water with high salinity, high chroma, and high COD, which seriously pollutes the environment, and the salt precipitation process brings into The high salt content reduces the purity of the dye and affects the solubility and colorability of the dye. Nanofiltration membrane treatment technology is a pressure-driven membrane separation process between ultrafiltration and reverse osmosis. The relative molecular mass of most water-soluble dyes is just within the range of the relative molecular mass of nanofiltration membranes. During the circulation of the solution through the nanofiltration membrane, part of the water and salt will pass through the membrane, while the dye molecules are retained by the membrane. By adding water to the system for washing, the salt content in the feed solution will gradually decrease.

Polysulfone polymer is an amorphous high-performance engineering polymer with excellent properties, such as high strength, good chemical stability and hydrolytic stability. A good solvent-resistant organic film material. Due to its high surface chemical energy, the hydrophilic property of the membrane surface is poor, resulting in serious membrane fouling. Membrane fouling is the primary problem affecting the membrane fouling process. It is manifested by the rapid decay of flux during membrane operation and the difficulty of cleaning and recovery. It is also the bottleneck that limits the wide application of membrane separation technology. water modified. At present, the commonly used methods to improve the hydrophilicity of membrane surface include adsorption modification method, surface coating modification method, blending modification method, low temperature plasma modification method, photografting modification method, etc. For the modification of polysulfone membranes, CN106179002A discloses a method for preparing microfiltration membranes by grafting polytertiary amines on polysulfone side chains. CN105817147A discloses a modified polysulfone membrane using polyethylene glycol and silica in combination. CN105771707A discloses an amphiphilic block polymer polycholine methacrylate-polymethyl methacrylate-polycholine methacrylate (PSBMA-b-PMMA-b-PSBMA) blending modification Polyethersulfone membrane with improved hydrophilicity.

In the prior art, polysulfone membranes have some defects:

1. Polysulfone membranes have poor hydrophilicity, and are easy to adsorb pollutants during use, resulting in small membrane flux, short life, easy blockage, and reduced treatment efficiency, which greatly limits its popularization and use;

2. The preparation methods of the existing polysulfone nanofiltration membranes all adopt the method of interfacial polymerization, the operation process is complicated, the solvent consumption is large, and the equipment utilization rate is low. It can be seen that the preparation of the polysulfone membranes in the prior art is to be further improved.

SUMMARY OF THE INVENTION

The purpose of the present invention is to further improve the hydrophilicity and separation performance of the polysulfone membrane, especially for sewage treatment, to provide a hydrophilic polysulfone membrane and a preparation method thereof. The proposed polysulfone anti-fouling composite membrane not only has high rejection rate, but also has good anti-fouling performance, and has potential development in the field of sewage treatment.

Technical scheme of the present invention:

The invention adopts two methods of blending modification method and surface coating modification method to modify the polysulfone membrane. By blending with acrylonitrile-maleic anhydride polymer, the hydrophilicity of the membrane is significantly improved, After modification by dopamine coating, the hydrophilic property of the membrane is further improved, and the pores on the surface of the membrane are modified by using the strong adhesion property of dopamine, which improves the separation effect of the membrane, and realizes that the pore size of the membrane changes from ultrafiltration to nanofiltration. The transformation of filtration, while effectively reducing the pore size of the membrane, further improves the hydrophilicity of the membrane.

The specific technical scheme of the present invention is: a hydrophilic polysulfone membrane, which is characterized by a composite membrane composed of a polysulfone polymer, acrylonitrile-maleic anhydride polymer, and dopamine coated on the composite membrane The thickness of the support layer of the composite membrane is 10-300 μm, the thickness of the separation layer is 0.1-0.5 μm, the thickness of the dopamine layer is about 50-500 nm, and the modified membrane molecular weight cut-off is 500-4,000Da.

Preferably, the above-mentioned polysulfone polymer is polysulfone, polyethersulfone, polyphenylsulfone or polyarylsulfone, wherein the molecular weight of polysulfone is 1,700-3,500 Da, the molecular weight of polyethersulfone is 1,000-6,020 Da, and the molecular weight of polyphenylsulfone is 3,000 ~5,000Da, the molecular weight of polyarylsulfone is 1,000~7,700Da.

The present invention also provides the preparation method of the above-mentioned hydrophilic polysulfone membrane, and its specific steps are as follows:

(A) Preparation of film-forming solution

Dissolve the polysulfone polymer, organic additive, inorganic additive and acrylonitrile-maleic anhydride polymer in an organic solvent, and mix evenly to prepare the raw material of the casting liquid, wherein the mass content of the polysulfone polymer is 15- 25%, the mass content of organic additives is 0.1-15%, the mass content of inorganic additives is 0.1-5%, the content of acrylonitrile-maleic anhydride polymer is 0.1-5%; the organic solvent is 50%-84.7%;

(B) Preparation of membranes

The preparation of membrane is divided into the preparation of flat membrane or hollow fiber membrane:

The preparation method of the flat film: at a temperature of 15-30° C. and a humidity of 30-70%, pour the film-forming liquid prepared in step (A) on a clean glass plate, and adjust the thickness of the scraper to be 10-300 μm, The speed of scraping the film is 5-50m·min ^-1 , and the residence time in the air is 3-20s. Put the scraped film together with the glass plate into the coagulation bath (deionized water), and control the temperature of the coagulation bath to be 10-50 ℃. After rinsing, a polysulfone composite membrane is obtained;

The preparation method of the hollow fiber membrane: at a temperature of 15 to 30° C. and a humidity of 30 to 70%, the support layer casting solution prepared in step (A) is used as the spinning solution, and the spinning solution and the core solution are injected simultaneously. Double-channel spinneret, in which the core liquid is injected into the inner core channel, the spinning liquid is injected into the outer channel, and the hollow fiber membrane embryo body is prepared by extrusion. In the bath (deionized water), control the temperature of the coagulation bath to be 10-50°C;

(C) Dopamine multiple times coating polysulfone composite membrane

Preparation of Tris (tris(hydroxymethyl)aminomethane)-HCl buffer solution: prepare 0.01～1mol·L ^-1 Tris solution, adjust pH to 1～9 with hydrochloric acid, then add dopamine to the buffer, the concentration of dopamine is 1～1～ 6g·L ^-1 , put the prepared composite membrane into the dopamine solution, put it into the shaker to shake for 6-24 hours, and then take out the membrane, or put it into the newly prepared dopamine solution for re-coating to obtain Hydrophilic polysulfone membrane.

Preferably, the organic additive is one or any combination of polyvinylpyrrolidone with a molecular weight of 10,000-360,000 Da or polyethylene glycol with a molecular weight of 200-10,000 Da.

Preferably, the above-mentioned inorganic additive is titanium oxide, aluminum oxide, zinc oxide, zirconium oxide or lithium chloride.

Preferably, the above-mentioned organic solvent is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide or acetone.

Preferably, during the preparation of the hollow fiber membrane, the extrusion rate of the core solution is 1-20 ml/min, and the extrusion rate of the spinning solution is 1-18 ml/min.

Preferably, the core liquid described in the preparation process of the hollow fiber membrane is a mixture of deionized water and a solvent; wherein the solvent is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone , dimethyl sulfoxide or acetone; the content of water in the core liquid accounts for 20-50%.

Preferably, the number of times of recoating in step C is 1 to 10 times.

The above-mentioned acrylonitrile-maleic anhydride polymer is preferably prepared by conventional aqueous polymerization:

Potassium persulfate (K ₂ S ₂ O ₈ ) and sodium sulfite (Na ₂ SO ₃ ) were used as chain initiators, and acrylonitrile (AN) and maleic anhydride (MAH) were used as monomers. The reaction was carried out at 70°C in a nitrogen atmosphere. to react. In a three-necked flask equipped with a reflux condenser, an air inlet pipe and a stirring device, AN, MAH, K ₂ S ₂ O ₈ , Na ₂ SO ₃ and deionized water (using 0.05 mol·L ^-1 of H ₂ SO ₄ to adjust the pH to 3), stir with a stirrer at a certain speed to mix the solution evenly, take out the precipitate after 5 h of reaction, wash it three times with absolute ethanol and deionized water in turn, vacuum filter it at 60 ° C Dry and weigh.

Beneficial effects:

(1) The acrylonitrile-maleic anhydride polymer contains a hydrophilic functional carboxyl group, which has good compatibility with polysulfone polymers, so that the prepared polysulfone membrane has good hydrophilicity and anti-pollution Good performance. During the phase inversion process, the hydrophilic segment of the acrylonitrile-maleic anhydride polymer will spontaneously migrate to the surface of the membrane for self-assembly, and the hydrophilicity and pollution resistance of the membrane are greatly improved. .

(2) Using dopamine to coat the composite membrane, on the one hand, due to the good hydrophilicity of dopamine, the anti-fouling performance of the membrane is further improved; on the other hand, due to the strong adhesion performance of dopamine, a layer of The dense layer plays the role of modifying the pore size of the membrane and improves the separation performance of the membrane.

Detailed ways

The present invention is further described below through specific examples, but the present invention is not limited thereto.

Example 1

The method prepares a hydrophilic polyphenylsulfone dye desalination membrane material. Polyvinylpyrrolidone with a molecular weight of 10,000Da, acrylonitrile-maleic anhydride, titanium dioxide and polyphenylsulfone with a molecular weight of 3,000Da were dissolved in N,N-dimethylformamide, and mixed uniformly to prepare the raw material of the casting liquid , wherein the mass content of polyvinylpyrrolidone is 15%, the mass content of polyphenylsulfone is 15%, the content of acrylonitrile-maleic anhydride is 5%, the content of titanium dioxide is 0.1%, and the content of N,N-dimethyl The mass content of formamide was 64.9%. The room temperature was controlled to be 15° C. and the humidity was 30%, the film-forming liquid was evenly poured onto the glass plate, the height of the scraper was adjusted to 10 μm, and the scraping speed was 5 m·min ⁻¹ . After scraping, wait for the membrane to stay in the air for 3s and then put it into a coagulation bath filled with deionized water (50°C). After the membrane body is solidified into a membrane and separated from the glass plate, rinse the membrane. Change the water every 4 hours and change 3 The membranes were then characterized for testing. Prepare 1 L of 0.01 mol·L ^-1 Tris buffer solution, adjust the pH to 1 with hydrochloric acid, add 1 g of dopamine to the buffer solution, put the prepared composite membrane into the dopamine solution, put it in a shaker for 24 hours, and take out Then put it into deionized water and shake it for 3 times.

The contact angle of the prepared composite membrane is 30°, the thickness of the support layer is 10 μm, the thickness of the separation layer is 0.1 μm, and the thickness of the dopamine layer is 50 nm. At 0.5MPa and 25℃, the pure water flux was measured with an ultrafiltration device of 20L·m ^-2 ·h ^-1 , the PEG cut-off molecular weight was 4,000Da, and the 100mg·L ^-1 direct red/NaCl salt solution was used to filter the salt ions. Passable with 80% rejection of direct red dye.

Example 2

The method prepares a hydrophilic polyphenylsulfone dye desalination membrane material. Polyvinylpyrrolidone with a molecular weight of 36,000Da, acrylonitrile-maleic anhydride, polyphenylsulfone with a molecular weight of 5,000Da and zirconium dioxide nanoparticles were dissolved in N,N-dimethylacetamide, and mixed uniformly to prepare The raw material of the casting liquid, wherein the mass content of polyvinylpyrrolidone is 0.1%, the mass content of polyphenylsulfone is 25%, the content of acrylonitrile-maleic anhydride is 0.1%, and the content of zirconium dioxide nanoparticles is 5% , the mass content of N,N-dimethylformamide is 69.8%. Control the room temperature to 30°C and the humidity to 70%. The prepared casting solution was used as a spinning solution, and a mixture of 80% acetone and 20% deionized water was injected into the inner core channel. The extrusion rate of the core solution was 20 ml/min, and the extrusion rate of the casting solution was 18 ml/min. minute. After an air interval of 20s, it entered a coagulation bath (10° C.) for curing to form a double-layered hollow fiber membrane, which was collected by a winder. The prepared hollow fiber membranes were immersed in deionized water, and the water was changed every 4 h, and the membranes were subjected to a characterization test after changing three times. Prepare 1 L of 1 mol·L ^-1 Tris buffer solution, adjust the pH to 9 with hydrochloric acid, add 2 g of dopamine to the buffer solution, put the prepared composite membrane into the dopamine solution, and put it into a shaker to shake and coat for 6 hours. The membrane was taken out, put into the freshly prepared dopamine solution again and coated again, and the cycle was coated for 10 times.

The contact angle of the prepared composite membrane is 20°, the thickness of the support layer is 250 μm, the thickness of the separation layer is 0.5 μm, and the thickness of the dopamine layer is 500 nm. At 0.5MPa and 25℃, the pure water flux was measured with an ultrafiltration device of 8L·m ^-2 ·h ^-1 , the PEG cut-off molecular weight was 500Da, and the 100mg·L ^-1 direct red/NaCl salt solution was used to filter the salt ions. Passed with 99% rejection of direct red dye.

Example 3

The method prepares a hydrophilic polysulfone dye desalination membrane material. Polysulfone with a molecular weight of 3,500Da, polyvinylpyrrolidone with a molecular weight of 55,000Da, acrylonitrile-maleic anhydride and inorganic particle zirconia were dissolved in dimethyl sulfoxide, and mixed uniformly to prepare the raw material of the casting solution. The mass content of sulfone is 25%, the content of acrylonitrile-maleic anhydride is 1%, the content of alumina is 2.5%, the content of polyvinylpyrrolidone is 15%, and the content of N-methylpyrrolidone is 56.5%. The room temperature was controlled to be 30° C. and the humidity was 70%, the film-forming liquid was evenly poured onto the glass plate, the height of the scraper was adjusted to 300 μm, and the scraping speed was 50 m·min ⁻¹ . After scraping, wait for the film to stay in the air for 15s, and then put it into a coagulation bath containing deionized water (25°C). After the film body is solidified into a film and separated from the glass plate, rinse it. Change the water every 4 hours, and change 3 The membranes were then characterized for testing. Prepare 1 L of 0.2 mol·L ^-1 Tris buffer solution, adjust the pH to 2 with hydrochloric acid, add 6 g of dopamine to the buffer solution, put the prepared composite membrane into the dopamine solution, and put it into the shaker to shake and coat for 10 hours. , take out the membrane, put it into the freshly prepared dopamine solution again and coat it again, and repeat the coating cycle for 9 times.

The contact angle of the prepared composite membrane is 20°, the thickness of the support layer is 300 μm, the thickness of the separation layer is 0.3 μm, and the thickness of the dopamine layer is 450 nm. At 0.5MPa and 25℃, the pure water flux was measured with an ultrafiltration device of 9L·m ^-2 ·h ^-1 , the PEG cut-off molecular weight was 550Da, and the 100mg·L ^-1 direct red/NaCl salt solution was used to filter the salt ions. Passed with 98% rejection of direct red dye.

Example 4

The method prepares a hydrophilic polysulfone dye desalination membrane material. Polysulfone with a molecular weight of 1,700Da, polyvinylpyrrolidone with a molecular weight of 360,000Da, acrylonitrile-maleic anhydride and aluminum oxide are dissolved in N-methylpyrrolidone, and mixed uniformly to prepare the raw material of the casting solution. Its mass content is 15%, the content of acrylonitrile-maleic anhydride is 5%, the content of zinc oxide is 3%, the content of polyvinylpyrrolidone is 8%, and the content of N-methylpyrrolidone is 69%. The room temperature was controlled to be 30° C. and the humidity was 70%. The prepared casting solution was used as a spinning solution, and a mixture of 70% acetone and 30% deionized water was injected into the inner core channel. The extrusion rate of the core liquid was 20 ml/min, and the extrusion rate of the casting liquid was 18 ml/min. After an air interval of 5 s, it entered a coagulation bath (30° C.) to solidify to form a double-layer hollow fiber membrane, which was collected by a winder. The prepared hollow fiber membranes were immersed in deionized water, and the water was changed every 4 h, and the membranes were subjected to a characterization test after changing three times. Prepare 1 L of 0.8 mol·L ^-1 Tris buffer solution, adjust the pH to 3 with hydrochloric acid, add 4 g of dopamine to the buffer solution, put the prepared composite membrane into the dopamine solution, put it in a shaker and shake it for 10 hours, then , take out the membrane, put it into the freshly prepared dopamine solution again and coat it again, and repeat the coating cycle for 8 times.

The contact angle of the prepared composite membrane is 30°, the thickness of the support layer is 250 μm, the thickness of the separation layer is 0.1 μm, and the thickness of the dopamine layer is 400 nm. At 0.5MPa and 25℃, the pure water flux was measured with an ultrafiltration device of 9L·m ^-2 ·h ^-1 , the PEG cut-off molecular weight was 600Da, and 100mg·L ^-1 direct red/NaCl salt solution was used to filter, the salt ions can be Passed with 98% rejection of direct red dye.

Example 5

The method prepares a hydrophilic polyethersulfone dye desalination membrane material. Polyethylene glycol with a molecular weight of 200Da, polyethersulfone with a molecular weight of 1,000Da, acrylonitrile-maleic anhydride and lithium chloride nanoparticles are dissolved in acetone, and mixed uniformly to prepare the raw material of the casting liquid, wherein the polyethylene The mass content of diol is 15%, the mass content of polyethersulfone is 15%, the content of acrylonitrile-maleic anhydride is 3%, the content of lithium chloride nanoparticles is 2%, and the mass content of acetone is 63% %. The room temperature was controlled to be 25° C. and the humidity was 40%. The prepared casting solution was used as a spinning solution, and a mixture of 60% acetone and 40% deionized water was injected into the inner core channel. The extrusion rate of the core liquid was 15 ml/min, and the extrusion rate of the casting liquid was 15 ml/min. After an air interval of 8 s, it entered a coagulation bath (50° C.) for curing to form a double-layer hollow fiber membrane, which was collected by a winder. The prepared hollow fiber membranes were immersed in deionized water, and the water was changed every 4 h, and the membranes were subjected to a characterization test after changing three times. Prepare 1 L of 0.01 mol·L ^-1 Tris buffer solution, adjust the pH to 4 with hydrochloric acid, add 3 g of dopamine to the buffer solution, put the prepared composite membrane into the dopamine solution, put it in a shaker and shake it for 20 hours, then , take out the membrane, put it into the freshly prepared dopamine solution again and coat it again, and repeat the coating cycle for 7 times.

The contact angle of the prepared composite membrane is 30°, the thickness of the support layer is 250 μm, the thickness of the separation layer is 0.1 μm, and the thickness of the dopamine layer is 350 nm. At 0.5MPa and 25℃, the pure water flux was measured with an ultrafiltration device of 12L·m ^-2 ·h ^-1 , the PEG cut-off molecular weight was 700Da, and the 100mg·L ^-1 direct red/NaCl salt solution was used to filter the salt ions. Passed with a rejection of 96% for direct red dye.

Example 6

The method prepares a hydrophilic polyarylsulfone dye desalination membrane material. Polyethersulfone with a molecular weight of 1,000Da, polyethylene glycol with a molecular weight of 6,000Da, inorganic nano-titanium oxide particles, and acrylonitrile-maleic anhydride are dissolved in N-methylpyrrolidone, and mixed uniformly to prepare the raw material of the casting solution , wherein the mass content of zinc oxide is 0.1%, the mass content of polyethersulfone is 15%, the content of acrylonitrile-maleic anhydride is 0.1%, the content of polyethylene glycol is 0.1%, and the content of N,N- The mass content of dimethylformamide was 84.7%. The room temperature was controlled to be 25° C. and the humidity was 40%, the film-forming liquid was evenly poured onto the glass plate, the height of the scraper was adjusted to 150 μm, and the scraping speed was 20 m·min ⁻¹ . After scraping, wait for the membrane to stay in the air for 8s, and then put it into a coagulation bath containing deionized water (25°C). After the membrane body is solidified into a membrane and separated from the glass plate, rinse it. The membranes were then characterized for testing. Prepare 1 L of 0.7 mol·L ^-1 Tris buffer solution, adjust the pH to 5 with hydrochloric acid, add 5 g of dopamine to the buffer solution, put the prepared composite membrane into the dopamine solution, and put it into a shaker to shake and coat for 24 hours. , take out the membrane, put it into the freshly prepared dopamine solution again and coat it again, and repeat the coating cycle for 6 times.

The contact angle of the prepared composite membrane is 26°, the thickness of the support layer is 150 μm, the thickness of the separation layer is 0.1 μm, and the thickness of the dopamine layer is 300 nm. At 0.5MPa and 25℃, the pure water flux was measured with an ultrafiltration device of 13L·m ^-2 ·h ^-1 , the PEG cut-off molecular weight was 850Da, and the 100mg·L ^-1 direct red/MgCl ₂ salt solution was used to filter the salt ions. Passable with 96% rejection of direct red dye.

Example 7

The method prepares a hydrophilic polyarylsulfone dye desalination membrane material. Inorganic zinc oxide particles, polyarylsulfone with a molecular weight of 7,700 Da, acrylonitrile-maleic anhydride and polyethylene glycol with a molecular weight of 6,000 are dissolved in acetone, and mixed uniformly to prepare the raw material of the casting liquid. The mass content of zinc particles is 5%, the mass content of polyarylsulfone is 25%, the content of acrylonitrile-maleic anhydride is 5%, the content of polyethylene glycol is 15%, and the content of N,N-dimethyl The mass content of formamide is 50%. The room temperature was controlled to be 25° C. and the humidity was 40%. The prepared casting solution was used as the spinning solution, and a mixture of 50% acetone and 50% deionized water was injected into the inner core channel. The extrusion rate of the core liquid was 10 ml/min, and the extrusion rate of the casting liquid was 10 ml/min. After an air interval of 12 s, it entered a coagulation bath (50° C.) to solidify to form a double-layer hollow fiber membrane, which was collected by a winder. The prepared hollow fiber membranes were immersed in deionized water, and the water was changed every 4 h, and the membranes were subjected to a characterization test after changing three times. Prepare 1 L of 0.9 mol·L ^-1 Tris buffer solution, adjust the pH to 6 with hydrochloric acid, add 3 g of dopamine to the buffer solution, put the prepared composite membrane into the dopamine solution, put it in a shaker and shake it for 10 hours, then , take out the membrane, put it into the freshly prepared dopamine solution again and coat it again, and repeat the coating cycle for 5 times.

The contact angle of the prepared composite membrane is 30°, the thickness of the support layer is 250 μm, the thickness of the separation layer is 0.1 μm, and the thickness of the dopamine layer is 250 nm. At 0.5MPa and 25℃, the pure water flux was measured with an ultrafiltration device of 14L·m ^-2 ·h ^-1 , the PEG cut-off molecular weight was 800Da, and 100mg·L ^-1 direct red/NaCl salt solution was used for filtration, and the salt ions could Passed with 95% rejection of direct red dye.

Example 8

The method prepares a hydrophilic polyethersulfone dye desalination membrane material. The zirconia nanoparticles, polyphenylsulfone with a molecular weight of 1,000Da, acrylonitrile-maleic anhydride and polyethylene glycol with a molecular weight of 10,000Da were dissolved in acetone, and mixed uniformly to prepare the raw material of the casting liquid. The mass content of pyrrolidone is 10%, the mass content of polyphenylsulfone is 20%, the mass content of zirconia nanoparticles is 1%, and the mass content of N,N-dimethylformamide is 69%. The room temperature was controlled to be 25° C. and the humidity was 40%. The prepared casting solution was used as a spinning solution, and a mixture of 70% acetone and 30% deionized water was injected into the inner core channel. The extrusion rate of the core liquid was 1 ml/min, and the extrusion rate of the casting liquid was 1 ml/min. After an air interval of 3 s, it entered a coagulation bath (50° C.) for curing to form a double-layer hollow fiber membrane, which was collected by a winder. The prepared hollow fiber membranes were immersed in deionized water, and the water was changed every 4 h, and the membranes were subjected to a characterization test after changing three times. Prepare 1 L of 0.01 mol·L ^-1 Tris buffer solution, adjust the pH to 8 with hydrochloric acid, add 3 g of dopamine to the buffer solution, put the prepared composite membrane into the dopamine solution, put it into a shaker and shake it for 18 hours, then , take out the membrane, put it into the freshly prepared dopamine solution again and coat it again, and repeat the coating cycle for 4 times.

The contact angle of the prepared composite membrane is 30°, the thickness of the support layer is 250 μm, the thickness of the separation layer is 0.1 μm, and the thickness of the dopamine layer is 200 nm. At 0.5MPa and 25℃, the pure water flux was measured with an ultrafiltration device of 15L·m ^-2 ·h ^-1 , the PEG cut-off molecular weight was 850Da, and filtered with 100mg·L ^-1 direct red/NaCl salt solution, the salt ions can be Passed with a rejection of 92% for direct red dye.

Claims (9)

1. a hydrophilic polysulfone type membrane is characterized in that the composite membrane that is made up of polysulfone type polymer, acrylonitrile-maleic anhydride polymer and the dopamine layer on the coating composite membrane are formed, wherein the composite membrane The thickness of the support layer is 10-300 μm, the thickness of the separation layer is 0.1-0.5 μm, the thickness of the dopamine layer is about 50-500 nm, and the molecular weight cut-off of the modified hydrophilic polysulfone membrane is 500-4,000 Da. 2 . The hydrophilic polysulfone membrane according to claim 1 , wherein the polysulfone polymer is polysulfone, polyethersulfone or polyarylsulfone, wherein the molecular weight of polysulfone is 1,700-3,500 Da, 2 . The molecular weight of polyethersulfone is 1,000 to 6,020 Da, and the molecular weight of polyarylsulfone is 1,000 to 7,700 Da. 3. a method for preparing the hydrophilic polysulfone membrane as claimed in claim 1, its concrete steps are as follows: (A) Preparation of film-forming solution Dissolve the polysulfone polymer, organic additive, inorganic additive and acrylonitrile-maleic anhydride polymer in an organic solvent, and mix evenly to prepare the raw material of the casting liquid, wherein the mass content of the polysulfone polymer is 15- 25%, the mass content of the organic additive is 0.1-15%, the mass content of the inorganic additive is 0.1-5%, the mass content of the acrylonitrile-maleic anhydride polymer is 0.1-5%; the mass content of the organic solvent is 50%～84.7%; (B) Preparation of membranes The preparation of membrane is divided into the preparation of flat membrane or hollow fiber membrane: The preparation method of the flat film: at a temperature of 15 to 30° C. and a humidity of 30 to 70%, pour the film-forming liquid prepared in step (A) on a glass plate, adjust the thickness of the scraper to be 10 to 300 μm, and scrape the film. The speed is 5～50m·min ^-1 , the residence time in the air is 3～20s, the scraped film and the glass plate are put into the coagulation bath, and the temperature of the coagulation bath is controlled to be 10～50℃. After rinsing, polysulfone is obtained. composite film; The preparation method of the hollow fiber membrane: at a temperature of 15-30° C. and a humidity of 30-70%, the casting solution prepared in step (A) is used as the spinning solution, and the spinning solution and the core solution are simultaneously injected into the dual channels Spinneret, wherein the core liquid is injected into the inner core channel, the spinning liquid is injected into the outer channel, and the hollow fiber membrane embryo body is prepared by extrusion. , control the coagulation bath temperature to 10 ~ 50 ℃; (C) Dopamine multiple times coating polysulfone composite membrane Preparation of Tris-HCl buffer: prepare 0.01～1mol·L ^-1 Tris solution, adjust the pH to 1～9 with hydrochloric acid, then add dopamine to the buffer, the concentration of dopamine is 1～6g·L ^-1 , the preparation The good composite membrane is put into the dopamine solution and shaken for 6 to 24 hours in a shaker. After that, the membrane is taken out or put into the newly prepared dopamine solution for recoating to obtain a hydrophilic polysulfone membrane. 4. The method according to claim 3, wherein the organic additive has a molecular weight of 10,000-360,000Da polyvinylpyrrolidone or one or any of several polyethylene glycols with a molecular weight of 200-10,000Da combination. 5. The method according to claim 3, wherein the inorganic additive is titanium oxide, aluminum oxide, zinc oxide, zirconium oxide or lithium chloride. 6. method according to claim 3 is characterized in that the organic solvent in step A is N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide or acetone. 7. The method according to claim 3, wherein the extrusion rate of the core liquid is 1-20 ml/min and the extrusion rate of the spinning liquid is 1-18 ml/min in the preparation process of the hollow fiber membrane. 8. The method according to claim 3, wherein the core liquid described in the preparation process of the hollow fiber membrane is a mixture of deionized water and a solvent; wherein the solvent is N,N-dimethylformamide, N,N -Dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide or acetone; the content of water in the core liquid accounts for 20-50%. 9 . The method according to claim 3 , wherein the number of recoating in step C is 1 to 10 times. 10 .